My 92 351W had a chronic misfire since day one and I replaced all the usual suspects including wires cap rotor and plugs, I even replaced the coil with little or no improvement.
I started researching the ICM and discovered the module would fail either partially setting up a misfire or totally and present a no start condition when the module reached a temperature of 248 degrees.
The ICM is usually mounted to the distributor and since the distributor shaft is bathed in hot oil that can reach upwards of 260 degrees I deducted that my module had partially failed causing the misfire.
So I bought s premium replacement ICM and remote mount heatsink to solve the overheating issue and opened the hood only to discover there was no module on the distributor as my 92 E150 already had the remotely mounted ICM and heatsink, this worried me at first because I knew there was no way the module could have overheated but just for ****s and giggles I replaced the module and fired it up....
The idle seemed a bit smoother so I gave it some throttle and it responded with a rumble that let me know she was running on all 8 once again..
Moral of the story, the ICM does not have to overheat to partially fail, in my case it was simply old age that caused the module to partially fail and setup a chronic misfire, lesson learned..

 

Good to have it all working as it should once again huh?

Some of the electronic-based ignition parts do need to have a somewhat sophisticated diagnostic tool to see exactly how its performing. Most of us don't own that sort of gear and don't know anyone trustworthy who does so occasionally we do have to parts swap in hopes of solving a problem.

Your learned lesson will be helpful to others along the way I'm sure---thanks for sharing your findings and solution too!

 

For more information please Google "Ford TFI Module National Class Settlement", the maximum temperature for the ICM is 257F.

 

Yes I have seen plenty of partially failed ICMs and they were different every time.